Variation in forage quality in subtropical thicket
- Nyembe, Khulisile Jacqueline
- Authors: Nyembe, Khulisile Jacqueline
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Biodiversity -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52088 , vital:43440
- Description: Several studies have assumed that the plant communities of the Subtropical Thicket biome are nutritious throughout the year. This is based on the observation that they are evergreen, palatable and grow on fertile soils; however this assumption has not been tested. Therefore the aim of this study was to assess forage quality variation in the Subtropical Thicket. This was done at three levels; first we measured the plant quality of dominant plant species in the diets of Thicket herbivores. Secondly, we measured the realised diet quality of Thicket herbivores through the analysis of faecal samples. Lastly we assessed the body condition of Thicket herbivores. The study was conducted at the Colchester (plant quality and diet quality) and Addo Main Camp (body condition assessment) sections of Addo Elephant National Park. To measure the food quality of Thicket plants we analysed 10 plants that are dominant in the diets of Thicket herbivores. To measure diet quality we collected faecal samples from ten herbivores with body mass ranging from 25 kg to 6000 kg. Plant quality results showed that only 30% of the sampled plants met the high energy goat diet protein requirements and that all the sampled plants did not meet the high energy goat diet fibre requirements. This indicates that Thicket plants are not as highly nutritious as they were thought to be. The principle components analysis together with overlapping confidence intervals showed that there was no significant difference between the summer plant samples and the winter plant samples. The faecal quality results showed that there was significant seasonal difference and that faecal diet quality was a function of body size. The body condition results showed that all the sampled herbivores lost condition in the cold dry months. The evidence from faecal diet quality and body condition assessment is sufficient for us to reject the assumption that Thicket forage is consistently nutritious throughout the year. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Nyembe, Khulisile Jacqueline
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Biodiversity -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52088 , vital:43440
- Description: Several studies have assumed that the plant communities of the Subtropical Thicket biome are nutritious throughout the year. This is based on the observation that they are evergreen, palatable and grow on fertile soils; however this assumption has not been tested. Therefore the aim of this study was to assess forage quality variation in the Subtropical Thicket. This was done at three levels; first we measured the plant quality of dominant plant species in the diets of Thicket herbivores. Secondly, we measured the realised diet quality of Thicket herbivores through the analysis of faecal samples. Lastly we assessed the body condition of Thicket herbivores. The study was conducted at the Colchester (plant quality and diet quality) and Addo Main Camp (body condition assessment) sections of Addo Elephant National Park. To measure the food quality of Thicket plants we analysed 10 plants that are dominant in the diets of Thicket herbivores. To measure diet quality we collected faecal samples from ten herbivores with body mass ranging from 25 kg to 6000 kg. Plant quality results showed that only 30% of the sampled plants met the high energy goat diet protein requirements and that all the sampled plants did not meet the high energy goat diet fibre requirements. This indicates that Thicket plants are not as highly nutritious as they were thought to be. The principle components analysis together with overlapping confidence intervals showed that there was no significant difference between the summer plant samples and the winter plant samples. The faecal quality results showed that there was significant seasonal difference and that faecal diet quality was a function of body size. The body condition results showed that all the sampled herbivores lost condition in the cold dry months. The evidence from faecal diet quality and body condition assessment is sufficient for us to reject the assumption that Thicket forage is consistently nutritious throughout the year. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
Using spatial explicit capture-recapture model to investigate the demography and spatial dynamics of lion prides in Pilanesberg National Park
- Authors: Bettings, Isabella Aletta
- Date: 2022-12
- Subjects: Lions--Behavior--South Africa , Animals tracks -- Pilanesberg National Park -- North West
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59655 , vital:62318
- Description: Lions are apex predators that play a vital role in the ecosystem. They regulate prey species through predation and other non-consumptive means. Factors that have influenced the decline of lion populations across Africa in the last half century, are loss of habitat, human wildlife conflict and the depletion of prey species. Extensive reintroductions of lions have been conducted across South Africa in order to restore their numbers in protected areas. The Pilanesberg National Park (PNP) was one of many protected areas that reintroduced lions. Their numbers were well documented by management until 2005 where they lost track of the population numbers. During this unfortunate period, there was an observed decline in prey numbers. The aim of this dissertation was to estimate the abundance, movement, and sex ratio of lions, in PNP. Abundance, movement, and sex ratio were determined by a three-month intensive lion survey. The location of each lion encounter was recorded on a mobile device which had an application installed called Cybertracker (v3). Photographs were taken of each Lion to build identification kits. For the data analysis, I used the Bayesian spatial explicit capture-recapture (SECR) model. This model takes time, space, and the robustness of an individual lion into account. Robustness is the measure of how well a lion maintains their functionality, when various stressors are applied (Harmsen, Foster, & Quigley, 2020). The estimated lion population in PNP was 44 lions (>1 year) with a density of 8.8 lions per 100 km2 . The estimated mean home range size of male lions was 279 km2 with a highest probability density (HPD) range of 179 – 385 km2 . The estimated mean home range of female lions was 191 km2 with a HPD range of 135 – 262 km2 . The larger home range size for male lions and smaller home range size for females is found v throughout the African continent in protected areas. The estimated sex ratio was 0.9♀:1♂, which is unexpected as PNP sex ratios between male and female lions is usually 2♀:1♂. A future sampling design for PNP was produced from the completed lion survey dataset. I drove a total of 7350 km and evaluated the influence of varied sampling efforts (i.e., kms driven) on precision estimates and relative bias for abundance, movement, and sex ratio. I found that a minimum of 4 000 km was needed to adequately estimate the lion abundance, movement, and sex ratio in this small fenced protected area. These findings can be used to help guide management to the most cost-effective sampling method and still obtain accurate estimates for monitoring lions. By showing management what is required for appropriate lion surveys this might help improve future monitoring. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Bettings, Isabella Aletta
- Date: 2022-12
- Subjects: Lions--Behavior--South Africa , Animals tracks -- Pilanesberg National Park -- North West
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59655 , vital:62318
- Description: Lions are apex predators that play a vital role in the ecosystem. They regulate prey species through predation and other non-consumptive means. Factors that have influenced the decline of lion populations across Africa in the last half century, are loss of habitat, human wildlife conflict and the depletion of prey species. Extensive reintroductions of lions have been conducted across South Africa in order to restore their numbers in protected areas. The Pilanesberg National Park (PNP) was one of many protected areas that reintroduced lions. Their numbers were well documented by management until 2005 where they lost track of the population numbers. During this unfortunate period, there was an observed decline in prey numbers. The aim of this dissertation was to estimate the abundance, movement, and sex ratio of lions, in PNP. Abundance, movement, and sex ratio were determined by a three-month intensive lion survey. The location of each lion encounter was recorded on a mobile device which had an application installed called Cybertracker (v3). Photographs were taken of each Lion to build identification kits. For the data analysis, I used the Bayesian spatial explicit capture-recapture (SECR) model. This model takes time, space, and the robustness of an individual lion into account. Robustness is the measure of how well a lion maintains their functionality, when various stressors are applied (Harmsen, Foster, & Quigley, 2020). The estimated lion population in PNP was 44 lions (>1 year) with a density of 8.8 lions per 100 km2 . The estimated mean home range size of male lions was 279 km2 with a highest probability density (HPD) range of 179 – 385 km2 . The estimated mean home range of female lions was 191 km2 with a HPD range of 135 – 262 km2 . The larger home range size for male lions and smaller home range size for females is found v throughout the African continent in protected areas. The estimated sex ratio was 0.9♀:1♂, which is unexpected as PNP sex ratios between male and female lions is usually 2♀:1♂. A future sampling design for PNP was produced from the completed lion survey dataset. I drove a total of 7350 km and evaluated the influence of varied sampling efforts (i.e., kms driven) on precision estimates and relative bias for abundance, movement, and sex ratio. I found that a minimum of 4 000 km was needed to adequately estimate the lion abundance, movement, and sex ratio in this small fenced protected area. These findings can be used to help guide management to the most cost-effective sampling method and still obtain accurate estimates for monitoring lions. By showing management what is required for appropriate lion surveys this might help improve future monitoring. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2022
- Full Text:
- Date Issued: 2022-12
Using information visualization to support the self-management of type 2 diabetes mellitus
- Authors: Nauder, Meggan Kate
- Date: 2022-04
- Subjects: Information visualization , Diabetics --Treatment --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55711 , vital:53409
- Description: The globally increasing number of individuals suffering from Type 2 Diabetes Mellitus (T2DM), a completely preventable incurable disease of the pancreas, highlights the need for an effective tool for users to understand the relationship between their behaviours and the effect that those behaviours can have on their blood glucose levels (BGLs). There are few Information Visualisation (IV) tools available that can be used to reduce the cognition required to understand correlations between behaviour and BGLs. Existing tools require time-consuming, lengthy inputs and provide simple visualisations that do not show correlations. This leads to ineffective self-management of T2DM. Information Visualisation (IV) techniques can be used to support effective self-management of T2DM and reduce the cognition required to interpret DM data. Suitable IV techniques were identified and used to visualize T2DM data to aid in the self-management of the disease. Temporal charts, i.e. The Bar, Pie and Line Chart as well as heat maps, were selected as the most appropriate IV techniques to visualize T2DM data as they support time-series data well. A prototype, MedicMetric was created as an IV tool for visualizing T2DM data. MedicMetric incorporated three designed charts, namely the Change Rate Line View, the Radial Progress View, and the Annotated Line View. The Change Rate Line View and Annotated Line View both used line IV techniques, while the Radial Progress View made use of the bar IV technique. The Change Rate Line View performed the worst overall. A usability evaluation was conducted to compare these techniques and to determine which technique is most suitable for visualizing T2DM data. The results leaned significantly in favour of the Annotated Line View. This view is most similar to the line charts typically used in other IV tools. For this reason, the MedicMetric app was briefly compared to the MySygr and Diabetes:M application. In effectiveness and efficiency, MedicMetric and MySugr obtained almost identical results. However, participants indicated that MedicMetric supported their tasks using the Visual Information Seeking Mantra (VISM) the best overall, with 100% of participants stating that they would prefer to use the MedicMetric application. Several usability problems were identified with the IV techniques and they were addressed shortly after the study was complete. Overall participants were most satisfied with the Annotated Line View. , Thesis (MSc) -- Faculty of Science, Computing Sciences, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Nauder, Meggan Kate
- Date: 2022-04
- Subjects: Information visualization , Diabetics --Treatment --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55711 , vital:53409
- Description: The globally increasing number of individuals suffering from Type 2 Diabetes Mellitus (T2DM), a completely preventable incurable disease of the pancreas, highlights the need for an effective tool for users to understand the relationship between their behaviours and the effect that those behaviours can have on their blood glucose levels (BGLs). There are few Information Visualisation (IV) tools available that can be used to reduce the cognition required to understand correlations between behaviour and BGLs. Existing tools require time-consuming, lengthy inputs and provide simple visualisations that do not show correlations. This leads to ineffective self-management of T2DM. Information Visualisation (IV) techniques can be used to support effective self-management of T2DM and reduce the cognition required to interpret DM data. Suitable IV techniques were identified and used to visualize T2DM data to aid in the self-management of the disease. Temporal charts, i.e. The Bar, Pie and Line Chart as well as heat maps, were selected as the most appropriate IV techniques to visualize T2DM data as they support time-series data well. A prototype, MedicMetric was created as an IV tool for visualizing T2DM data. MedicMetric incorporated three designed charts, namely the Change Rate Line View, the Radial Progress View, and the Annotated Line View. The Change Rate Line View and Annotated Line View both used line IV techniques, while the Radial Progress View made use of the bar IV technique. The Change Rate Line View performed the worst overall. A usability evaluation was conducted to compare these techniques and to determine which technique is most suitable for visualizing T2DM data. The results leaned significantly in favour of the Annotated Line View. This view is most similar to the line charts typically used in other IV tools. For this reason, the MedicMetric app was briefly compared to the MySygr and Diabetes:M application. In effectiveness and efficiency, MedicMetric and MySugr obtained almost identical results. However, participants indicated that MedicMetric supported their tasks using the Visual Information Seeking Mantra (VISM) the best overall, with 100% of participants stating that they would prefer to use the MedicMetric application. Several usability problems were identified with the IV techniques and they were addressed shortly after the study was complete. Overall participants were most satisfied with the Annotated Line View. , Thesis (MSc) -- Faculty of Science, Computing Sciences, 2022
- Full Text:
- Date Issued: 2022-04
Ureaplasma species in the placenta and histopathology associated with preterm birth
- Authors: Sprong, Kaitlin Elizabeth
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54128 , vital:46310
- Description: The Eastern Cape province is known for its high perinatal morbidity and mortality rate. Studies from other countries indicate that Ureaplasma spp. have been associated with clinical chorioamnionitis, spontaneous preterm labor and preterm premature rupture of the fetal membranes. The prevalence of Ureaplasma urealyticum, Ureaplasma parvumand Mycoplasma hominisin the placenta and its role in preterm birth is unknown in South Africa. Objectives The objectives of this study were to: (i) analyze placental histology, maternal and neonatal outcomes and clinical presentation of preterm birth, (ii) detect Ureaplasma spp. and M. hominisin the placenta from cases of preterm birth, (iii) determine antibiotic susceptibility profiles of Ureaplasma spp. isolates and investigate mechanisms of antibiotic resistance, (iv) characterize the microbial diversity in the placenta using 16S rRNA next generation sequencing and(v) review pathologies to ascertain whether there is any association between Ureaplasma spp. in the placenta and adverse maternal, obstetric and neonatal outcomes. iiiABSTRACTBackground The Eastern Cape province is known for its high perinatal morbidity and mortality rate. Studies from other countries indicate that Ureaplasmaspp. have been associated with clinical chorioamnionitis, spontaneous preterm labor and preterm premature rupture of the fetal membranes. The prevalenceof Ureaplasmaurealyticum,UreaplasmaparvumandMycoplasmahominisin the placenta andits role in preterm birth is unknown in South Africa. Objectives The objectives of this study were to: (i) analyze placental histology, maternal and neonatal outcomes and clinical presentation of preterm birth, (ii) detect Ureaplasmaspp. and M. hominisin the placenta from cases of preterm birth, (iii) determine antibiotic susceptibility profiles of Ureaplasmaspp. isolates and investigate mechanisms of antibiotic resistance, (iv) characterize the microbial diversity in the placenta using 16S rRNA next generation sequencing and(v) review pathologies to ascertain whether there is any association between Ureaplasmaspp. inthe placenta and adverse maternal, obstetric and neonatal outcomes. MethodsPlacentas were collected from patients presenting with preterm birth (n=100; 28-34 weeks gestational age) and term birth (n=20; >38 weeks) regardless of the APGAR score. Placentas were submitted for histopathology and used for detection of Ureaplasmaspp. by culture (U9 broth, MycoDuo kits;BioRad) and PCR (DNA was extracted from culture and homogenized placental tissue). Antibiotic susceptibility profiles of Ureaplasmaspp isolates were determined by the SIR Antibiogram kit (BioRad) and microbroth dilution method. Molecular mechanisms of resistance were ascertained by PCR amplification of target genes. Placentas were sent to National Health Laboratory Servicesfor routine histopathology. Next generation sequencing was performed on 16S rRNA amplicons from placental DNA for analysis of microbial diversity. , Thesis (PhD) -- Faculty of Science, Journalsim and Media Studies, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Sprong, Kaitlin Elizabeth
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54128 , vital:46310
- Description: The Eastern Cape province is known for its high perinatal morbidity and mortality rate. Studies from other countries indicate that Ureaplasma spp. have been associated with clinical chorioamnionitis, spontaneous preterm labor and preterm premature rupture of the fetal membranes. The prevalence of Ureaplasma urealyticum, Ureaplasma parvumand Mycoplasma hominisin the placenta and its role in preterm birth is unknown in South Africa. Objectives The objectives of this study were to: (i) analyze placental histology, maternal and neonatal outcomes and clinical presentation of preterm birth, (ii) detect Ureaplasma spp. and M. hominisin the placenta from cases of preterm birth, (iii) determine antibiotic susceptibility profiles of Ureaplasma spp. isolates and investigate mechanisms of antibiotic resistance, (iv) characterize the microbial diversity in the placenta using 16S rRNA next generation sequencing and(v) review pathologies to ascertain whether there is any association between Ureaplasma spp. in the placenta and adverse maternal, obstetric and neonatal outcomes. iiiABSTRACTBackground The Eastern Cape province is known for its high perinatal morbidity and mortality rate. Studies from other countries indicate that Ureaplasmaspp. have been associated with clinical chorioamnionitis, spontaneous preterm labor and preterm premature rupture of the fetal membranes. The prevalenceof Ureaplasmaurealyticum,UreaplasmaparvumandMycoplasmahominisin the placenta andits role in preterm birth is unknown in South Africa. Objectives The objectives of this study were to: (i) analyze placental histology, maternal and neonatal outcomes and clinical presentation of preterm birth, (ii) detect Ureaplasmaspp. and M. hominisin the placenta from cases of preterm birth, (iii) determine antibiotic susceptibility profiles of Ureaplasmaspp. isolates and investigate mechanisms of antibiotic resistance, (iv) characterize the microbial diversity in the placenta using 16S rRNA next generation sequencing and(v) review pathologies to ascertain whether there is any association between Ureaplasmaspp. inthe placenta and adverse maternal, obstetric and neonatal outcomes. MethodsPlacentas were collected from patients presenting with preterm birth (n=100; 28-34 weeks gestational age) and term birth (n=20; >38 weeks) regardless of the APGAR score. Placentas were submitted for histopathology and used for detection of Ureaplasmaspp. by culture (U9 broth, MycoDuo kits;BioRad) and PCR (DNA was extracted from culture and homogenized placental tissue). Antibiotic susceptibility profiles of Ureaplasmaspp isolates were determined by the SIR Antibiogram kit (BioRad) and microbroth dilution method. Molecular mechanisms of resistance were ascertained by PCR amplification of target genes. Placentas were sent to National Health Laboratory Servicesfor routine histopathology. Next generation sequencing was performed on 16S rRNA amplicons from placental DNA for analysis of microbial diversity. , Thesis (PhD) -- Faculty of Science, Journalsim and Media Studies, 2021
- Full Text:
- Date Issued: 2021-12
Upwelling over submarine canyons: an in-situ and modelling approach
- Authors: Rautenbach, Gustav
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Oceanography -- Research -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52078 , vital:43442
- Description: The iSimangaliso Wetland Park, located along the coastline of northern KwaZulu-Natal (KZN), hosts South Africa's only tropical coral reef system and is clustered with submarine canyons. These ecosystems support a flourishing diving and pelagic sportfishing industry in the area that contributes tens of millions of rand to the South African Gross Domestic Profit (GDP) annually as well as to provide income and job security for the majority of the local residents. Understanding the oceanographic dynamics, particularly upwelling events, will improve current knowledge of how the ecosystem works and may enhance conservation techniques. The upwelling events within the iSimangaliso Wetland Park results in the influx of cold and nutrient rich waters that supports biological productivity in the area. The complex oceanography, dominated by the Northern Agulhas Current and mesoscale eddies that stem from the Mozambique Channel and South East Madagascar Current (SEMC) is understudied and lacks understanding. This thesis aims to build upon the current knowledge of the upwelling events over the submarine canyons and the concurrent influence on the Mixed Layer Depth (MLD). At the submarine canyons, six anomalous cooling events were identified from surface and subsurface measurements extracted from the Operational Sea Surface Temperature and Ice Analysis (OSTIA) Sea Surface Temperature (SST) and from data collected using Underwater Temperature Recorders (UTRs) over a 12-month period. Depth-integrated lagged correlations showed a 2-to-7-hour lag period from the deep to shallow stations, suggesting that the anomalous cooling events are in fact upwelling events. Wind measurements from the Mbazwana Weather Station and snapshots of sea-level anomalies illustrated that the weaker and shorter upwelling events are driven either by alongshore wind stress or a cyclonic eddy event solely; whereas the stronger event was driven by the combination of both forcing mechanisms. An idealized canyon ocean model is used to interrogate the two forcing mechanisms more fully and showed that the most intense upwelling events are driven by the combined effect of upwelling-favourable alongshore wind stress and a cyclonic eddy which results in strong upward vertical velocity anomalies and the greatest shallowing (6.88 m) of the MLD. With the contribution of the in-situ measurements as a baseline study it is apparent that the idealised model does provide an improved understanding of the upwelling events and forcing mechanism over the submarine canyons within the iSimangaliso Wetland Park. , Thesis (MSc) -- Faculty of Science, Ocean Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Rautenbach, Gustav
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Oceanography -- Research -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52078 , vital:43442
- Description: The iSimangaliso Wetland Park, located along the coastline of northern KwaZulu-Natal (KZN), hosts South Africa's only tropical coral reef system and is clustered with submarine canyons. These ecosystems support a flourishing diving and pelagic sportfishing industry in the area that contributes tens of millions of rand to the South African Gross Domestic Profit (GDP) annually as well as to provide income and job security for the majority of the local residents. Understanding the oceanographic dynamics, particularly upwelling events, will improve current knowledge of how the ecosystem works and may enhance conservation techniques. The upwelling events within the iSimangaliso Wetland Park results in the influx of cold and nutrient rich waters that supports biological productivity in the area. The complex oceanography, dominated by the Northern Agulhas Current and mesoscale eddies that stem from the Mozambique Channel and South East Madagascar Current (SEMC) is understudied and lacks understanding. This thesis aims to build upon the current knowledge of the upwelling events over the submarine canyons and the concurrent influence on the Mixed Layer Depth (MLD). At the submarine canyons, six anomalous cooling events were identified from surface and subsurface measurements extracted from the Operational Sea Surface Temperature and Ice Analysis (OSTIA) Sea Surface Temperature (SST) and from data collected using Underwater Temperature Recorders (UTRs) over a 12-month period. Depth-integrated lagged correlations showed a 2-to-7-hour lag period from the deep to shallow stations, suggesting that the anomalous cooling events are in fact upwelling events. Wind measurements from the Mbazwana Weather Station and snapshots of sea-level anomalies illustrated that the weaker and shorter upwelling events are driven either by alongshore wind stress or a cyclonic eddy event solely; whereas the stronger event was driven by the combination of both forcing mechanisms. An idealized canyon ocean model is used to interrogate the two forcing mechanisms more fully and showed that the most intense upwelling events are driven by the combined effect of upwelling-favourable alongshore wind stress and a cyclonic eddy which results in strong upward vertical velocity anomalies and the greatest shallowing (6.88 m) of the MLD. With the contribution of the in-situ measurements as a baseline study it is apparent that the idealised model does provide an improved understanding of the upwelling events and forcing mechanism over the submarine canyons within the iSimangaliso Wetland Park. , Thesis (MSc) -- Faculty of Science, Ocean Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
Uptake and storage of nutrients by primary producers in the Swartkops Estuary
- Authors: Whitfield, Emily Cailyn
- Date: 2022-12
- Subjects: Estuarine ecology --South Africa --Swartkops River Estuary , Eutrophication—Research
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59611 , vital:62195
- Description: Estuaries occur at the interface between the terrestrial and marine environment and as such act as the last ‘filtering’ mechanism prior to nutrient pollution entering the adjacent ocean. This study focused on the Swartkops Estuary which is eutrophic and requires the removal of nutrients. The role of phytoplankton as nutrient filters and storage of nutrients by seagrass and salt marsh was investigated. This study found that phytoplankton temporarily took up a large percentage of dissolved inorganic nitrogen (max. 99%) and dissolved silica (max. 76%) and limited amounts of dissolved inorganic phosphorus (max. 18%). The amount of carbon, nitrogen and phosphorus stored by the salt marsh species Spartina maritima and Salicornia tegetaria and the seagrass species Zostera capensis were determined. It was found that the salt marsh grass Spartina maritima stored the most nutrients (149.61 ± 16.59 N g m-2 ; 105.44 ± 13.41 P g m-2 ; 1690.52 ± 168.90 C g m-2 ), while for the salt marsh succulent Salicornia tegetaria less nutrients were stored (27.01 ± 4.17 N g m-2 ; 22.97 ± 3.21 P g m-2 ; 458.66 ± 69.43 C g m-2 ). Zostera capensis also acted as a nutrient store (22.17 ± 6.94 N g m-2 ; 23.75 ± 4.70 P g m-2 ; 221.10 ± 26.74 C g m-2 ). The macrophytes were able to store nutrients for longer periods and thus prevent these nutrients from being exported into the adjacent ocean. On the contrary, phytoplankton uptake was temporary as the nutrients are released once the bloom decays. Without intervention there will be an increase of harmful algal blooms (HABs) and fish kills in the eutrophic Swartkops Estuary. Nutrient input from upstream wastewater treatment works, canals and stormwater run-off must be reduced. Conservation and management of the seagrass and salt marsh habitats is needed to ensure the long-term storage of nutrients , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Whitfield, Emily Cailyn
- Date: 2022-12
- Subjects: Estuarine ecology --South Africa --Swartkops River Estuary , Eutrophication—Research
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59611 , vital:62195
- Description: Estuaries occur at the interface between the terrestrial and marine environment and as such act as the last ‘filtering’ mechanism prior to nutrient pollution entering the adjacent ocean. This study focused on the Swartkops Estuary which is eutrophic and requires the removal of nutrients. The role of phytoplankton as nutrient filters and storage of nutrients by seagrass and salt marsh was investigated. This study found that phytoplankton temporarily took up a large percentage of dissolved inorganic nitrogen (max. 99%) and dissolved silica (max. 76%) and limited amounts of dissolved inorganic phosphorus (max. 18%). The amount of carbon, nitrogen and phosphorus stored by the salt marsh species Spartina maritima and Salicornia tegetaria and the seagrass species Zostera capensis were determined. It was found that the salt marsh grass Spartina maritima stored the most nutrients (149.61 ± 16.59 N g m-2 ; 105.44 ± 13.41 P g m-2 ; 1690.52 ± 168.90 C g m-2 ), while for the salt marsh succulent Salicornia tegetaria less nutrients were stored (27.01 ± 4.17 N g m-2 ; 22.97 ± 3.21 P g m-2 ; 458.66 ± 69.43 C g m-2 ). Zostera capensis also acted as a nutrient store (22.17 ± 6.94 N g m-2 ; 23.75 ± 4.70 P g m-2 ; 221.10 ± 26.74 C g m-2 ). The macrophytes were able to store nutrients for longer periods and thus prevent these nutrients from being exported into the adjacent ocean. On the contrary, phytoplankton uptake was temporary as the nutrients are released once the bloom decays. Without intervention there will be an increase of harmful algal blooms (HABs) and fish kills in the eutrophic Swartkops Estuary. Nutrient input from upstream wastewater treatment works, canals and stormwater run-off must be reduced. Conservation and management of the seagrass and salt marsh habitats is needed to ensure the long-term storage of nutrients , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
Top-down control by grapsoid crabs in South African estuarine salt marshes
- Authors: Smith, Leigh-Ann
- Date: 2023-04
- Subjects: Salt marsh ecology – South Africa , Crabs --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61223 , vital:69807
- Description: Salt marshes are one of the most productive ecosystems globally. These ‘blue carbon’ habitats are in many respects resilient to climate change effects, able to track sea level rise and act as carbon sinks. Since salt marshes are economically and ecologically essential habitats (for example providing foraging grounds for invertebrates, fish, birds and humans), understanding the processes that control their structure is crucial to best maintain ecosystem services provided by these habitats. For decades the importance of top-down forces, such as grazing, has not been recognised as being important in controlling salt marsh plant productivity. Rather, bottom-up forces, such as the availability of oxygen, was thought to be the main constraint to primary production. Therefore, a better understanding of salt marsh ecosystem dynamics and whether grazer control exists is needed. Although grazer top-down control has been demonstrated in salt marshes in locations such as the United States, this has not been investigated in South Africa. This is a crucial knowledge gap locally considering the importance of salt marsh ecosystems. The aim of this study was therefore to determine what role consumers play in structuring South Africa’s estuarine salt marsh vegetation, thereby also contextualising this process internationally. In order to achieve this, the abundance of grapsoid crabs was estimated and related to key salt marsh features, such as Spartina maritima stem height and stem density, which was quantified from observational surveys. Sampling took place at the beginning and end of the early-spring and late-summer growth period (September 2021 and April 2022) in the Knysna, Kromme and Swartkops estuaries. If a correlation was observed between crab density and salt marsh features, it was important to determine whether they consume the salt marsh vegetation or if the effect was due to their burrowing activities. Hence, the diet of grapsoid crabs was investigated using stable isotope and gut content analysis. To examine the importance of crab grazing in controlling the growth of salt marsh vegetation, crab abundance was manipulated in situ by means of exclusion cages. This experiment ran for five months in the Kromme Estuary, from November 2021 to March 2022 over the salt marsh growing season. An ex situ feeding experiment was also conducted on 30 crab specimens collected from the Kromme Estuary, during May 2022. These crabs were starved for 48 hours and thereafter fed different components of Spartina (growing and dead blades, and roots and rhizomes). The food consumed was quantified as the change in plant length and dry weight after 48 hours, which gave a maximum grazing rate for the different food sources. It was found that crabs are having a minimal impact on the salt marsh vegetation structure. Spartina maritima does form an important component of the diet of grapsoid crabs, however, this is not their only source of food, and possibly not their preferred source of food. They are however contributing to sediment properties through their burrowing activities. The iii ex situ feeding experiment showed that grapsoid crabs can consume all vegetative components of Spartina, with a significantly greater amount of roots and rhizomes consumed. There was no consistent effect in terms of the exclusion of grazers, indicating that other mitigating factors could be reducing the impacts of grapsoid exclusion in situ. Together, these findings contribute knowledge that can be used to inform conservation by quantifying what the salt marsh risks losing in the absence or overabundance of crabs, as has occurred elsewhere globally. These results influence how salt marshes are managed, and highlight how not recognising the importance of consumers, such as crabs, could misalign management objectives. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2023-04
- Authors: Smith, Leigh-Ann
- Date: 2023-04
- Subjects: Salt marsh ecology – South Africa , Crabs --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61223 , vital:69807
- Description: Salt marshes are one of the most productive ecosystems globally. These ‘blue carbon’ habitats are in many respects resilient to climate change effects, able to track sea level rise and act as carbon sinks. Since salt marshes are economically and ecologically essential habitats (for example providing foraging grounds for invertebrates, fish, birds and humans), understanding the processes that control their structure is crucial to best maintain ecosystem services provided by these habitats. For decades the importance of top-down forces, such as grazing, has not been recognised as being important in controlling salt marsh plant productivity. Rather, bottom-up forces, such as the availability of oxygen, was thought to be the main constraint to primary production. Therefore, a better understanding of salt marsh ecosystem dynamics and whether grazer control exists is needed. Although grazer top-down control has been demonstrated in salt marshes in locations such as the United States, this has not been investigated in South Africa. This is a crucial knowledge gap locally considering the importance of salt marsh ecosystems. The aim of this study was therefore to determine what role consumers play in structuring South Africa’s estuarine salt marsh vegetation, thereby also contextualising this process internationally. In order to achieve this, the abundance of grapsoid crabs was estimated and related to key salt marsh features, such as Spartina maritima stem height and stem density, which was quantified from observational surveys. Sampling took place at the beginning and end of the early-spring and late-summer growth period (September 2021 and April 2022) in the Knysna, Kromme and Swartkops estuaries. If a correlation was observed between crab density and salt marsh features, it was important to determine whether they consume the salt marsh vegetation or if the effect was due to their burrowing activities. Hence, the diet of grapsoid crabs was investigated using stable isotope and gut content analysis. To examine the importance of crab grazing in controlling the growth of salt marsh vegetation, crab abundance was manipulated in situ by means of exclusion cages. This experiment ran for five months in the Kromme Estuary, from November 2021 to March 2022 over the salt marsh growing season. An ex situ feeding experiment was also conducted on 30 crab specimens collected from the Kromme Estuary, during May 2022. These crabs were starved for 48 hours and thereafter fed different components of Spartina (growing and dead blades, and roots and rhizomes). The food consumed was quantified as the change in plant length and dry weight after 48 hours, which gave a maximum grazing rate for the different food sources. It was found that crabs are having a minimal impact on the salt marsh vegetation structure. Spartina maritima does form an important component of the diet of grapsoid crabs, however, this is not their only source of food, and possibly not their preferred source of food. They are however contributing to sediment properties through their burrowing activities. The iii ex situ feeding experiment showed that grapsoid crabs can consume all vegetative components of Spartina, with a significantly greater amount of roots and rhizomes consumed. There was no consistent effect in terms of the exclusion of grazers, indicating that other mitigating factors could be reducing the impacts of grapsoid exclusion in situ. Together, these findings contribute knowledge that can be used to inform conservation by quantifying what the salt marsh risks losing in the absence or overabundance of crabs, as has occurred elsewhere globally. These results influence how salt marshes are managed, and highlight how not recognising the importance of consumers, such as crabs, could misalign management objectives. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2023-04
Thiazole derivatives as potential hiv-1 protease inhibitors
- Authors: Hlongwe, Zola
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Enzyme kinetics
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52116 , vital:43427
- Description: Series of compounds were screened using Schrodinger suite (Maestro). The DFT calculations were used for geometry optimization of the ligands using the B3YLYP functional and 6-31G basis set, and these structures were used for docking studies. Maestro was used to predict the activity of thiazole derivatives against HIV-1 protease. The range of estimated inhibition constants for these thiazole derivatives (65 nM-5 μM) indicate moderate to weak activity against HIV-1 protease, given that the activity of current protease inhibitors is typically found have experimental inhibition constants around 0.1-2.0 nM. Twenty compounds were selected based on the docking results and they were synthesized and characterized by NMR, FT-IR and elemental analysis. The cytotoxicity studies were done at two different concentrations (100 μM and 10 μM), using the brine shrimp bioassay. All compounds were highly toxic at 100 μM, with the percentage mortality between 20 to 75%. Eight compounds were selected for the enzyme bioassay based on the results obtained from lower concentration (10 μM). In the enzyme inhibition studies, the profile of HIV-1 activity was done at different inhibitor concentrations (800 μM – 10 μM) by measuring the cleavage of the synthetic substrate (Abz-Thr-lle-PNO2Phe=Gln-Arg-NH2) at excitation wavelength of 345/490 nm using fluorescence. Ligands 5 (unsubstituted derivative), 7 (4-nitro derivative) and 16 (4-methoxy derivative) gave percentage inhibition of 39, 45 and 42%, and this activity was very low compared to the activity of the positive control ritonavir (85% enzyme inhibition). Ligands 8 (4-methoxy derivative) and 12 (4-methoxy derivative) gave enzyme inhibition of 70% and 75%. These results suggest that the presence of the methoxy substituents ii increases activity of these compounds against HIV-1 protease. Most of the compounds gave good IC50 values between 12.5-42.7 nM. The bromo-substituted ligand 7 gave the lowest IC50 (12.5 nM). Ligand 11 also gave a good IC50 value of 14.86 nM. The bromo-substituted derivatives showed to be very active compared to other types of thiazole derivatives. Enzyme kinetics were carried out to compare the inhibition constants obtained via computational modelling. Ligand 7 (4-methoxy derivatives) binds better in the active site of HIV-1 protease than other compounds in Class B, with Ki = 50 nM, Km = 23.8 Nm and Vmax = 83.3 nM/min. The unsubstituted (L5), 4-bromo (L7) and 4-nitro (L8) substituted compounds gave inhibition constants of 100 to 112 nM. The in vitro testing yielded higher activity than that determined in silico. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Hlongwe, Zola
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Enzyme kinetics
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52116 , vital:43427
- Description: Series of compounds were screened using Schrodinger suite (Maestro). The DFT calculations were used for geometry optimization of the ligands using the B3YLYP functional and 6-31G basis set, and these structures were used for docking studies. Maestro was used to predict the activity of thiazole derivatives against HIV-1 protease. The range of estimated inhibition constants for these thiazole derivatives (65 nM-5 μM) indicate moderate to weak activity against HIV-1 protease, given that the activity of current protease inhibitors is typically found have experimental inhibition constants around 0.1-2.0 nM. Twenty compounds were selected based on the docking results and they were synthesized and characterized by NMR, FT-IR and elemental analysis. The cytotoxicity studies were done at two different concentrations (100 μM and 10 μM), using the brine shrimp bioassay. All compounds were highly toxic at 100 μM, with the percentage mortality between 20 to 75%. Eight compounds were selected for the enzyme bioassay based on the results obtained from lower concentration (10 μM). In the enzyme inhibition studies, the profile of HIV-1 activity was done at different inhibitor concentrations (800 μM – 10 μM) by measuring the cleavage of the synthetic substrate (Abz-Thr-lle-PNO2Phe=Gln-Arg-NH2) at excitation wavelength of 345/490 nm using fluorescence. Ligands 5 (unsubstituted derivative), 7 (4-nitro derivative) and 16 (4-methoxy derivative) gave percentage inhibition of 39, 45 and 42%, and this activity was very low compared to the activity of the positive control ritonavir (85% enzyme inhibition). Ligands 8 (4-methoxy derivative) and 12 (4-methoxy derivative) gave enzyme inhibition of 70% and 75%. These results suggest that the presence of the methoxy substituents ii increases activity of these compounds against HIV-1 protease. Most of the compounds gave good IC50 values between 12.5-42.7 nM. The bromo-substituted ligand 7 gave the lowest IC50 (12.5 nM). Ligand 11 also gave a good IC50 value of 14.86 nM. The bromo-substituted derivatives showed to be very active compared to other types of thiazole derivatives. Enzyme kinetics were carried out to compare the inhibition constants obtained via computational modelling. Ligand 7 (4-methoxy derivatives) binds better in the active site of HIV-1 protease than other compounds in Class B, with Ki = 50 nM, Km = 23.8 Nm and Vmax = 83.3 nM/min. The unsubstituted (L5), 4-bromo (L7) and 4-nitro (L8) substituted compounds gave inhibition constants of 100 to 112 nM. The in vitro testing yielded higher activity than that determined in silico. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
The use of ambient seismic noise to investigate internal changes in a tailings storage facility and to image the subsurface geology in the Cradock area of the Eastern Cape
- Authors: Kunjwa, Thulisile
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53642 , vital:45690
- Description: Passive seismic interferometry is a process by which ambient noise data recorded at different seismic stations can be cross-correlated to estimate Green's functions. In the past, both surface waves and body waves have successfully been extracted by cross-correlation of ambient noise data on both regional and global scales. Recent advancements in ambient seismic noise techniques have the potential to provide new methods for subsurface imaging and monitoring. The ambient noise data processing procedure divides into four principal phases: (1) single station data preparation, (2) cross-correlation and temporal stacking, (3) measurement of dispersion curves and (4) inversion of dispersion curves to obtain 1-D shear wave profiles and computation of 2-D shear wave velocity cross-section. The purpose of this study is to investigate whether ambient seismic noise can be used to image and detect internal changes within a mine tailings dam wall and to image the subsurface geology of part of the Eastern Cape Karoo near Cradock. In the first experiment, the investigation consisted of continuous ambient noise data recordings over a period of 3 days with 20 three-component short period geophones. The geophones were deployed over a survey wall of roughly 100 m in length at the Harmony Gold mine tailings dam in Welkom. In the second experiment, the investigation consisted of data recordings over a period of 35 days. The geophones were deployed in Cradock. The first phase of the data processing procedure included de-trending, de-meaning and band-pass filtering the data. This was done to ensure that any long period trends associated with instrument glitches are removed from the data. A spectrogram was then computed to view the spectrum of frequencies in the signal and to check if the filter that was designed was able to cut off the unwanted frequencies. The horizontal and vertical components of the ambient noise data were cross-correlated and picked between sensor pairs to create surface wave dispersion curves. Subsequently, the dispersion curves were inverted to estimate the shear wave velocity of the dam wall and subsurface as a function of depth. The computed cross sections of shear wave velocity indicated a low-velocity zone between 2 and 10 m below the surface on the dam wall, this suggested that the phreatic surface is much closer to surface in this area. In the second experiment, the interpolated shear wave velocity profiles indicated that there is a layer of low velocity zone between depths 250 to 300 m below the surface. The cross-correlations were also used to compute group velocity maps from periods 1.5 seconds to 30 seconds. The group velocity maps showed various high and low velocity anomalies. The high velocity zones observed on the eastern section of the map were interpreted as evidence of dolerite intrusions. The low velocity zones observed in the western and southern sections of the map interpreted as Karoo sediments that belong to the Adelaide Subgroup which is dominated by mudstones. , Thesis (MSc) -- Faculty of Science, Department of Geosciences (Geology and Geography), 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Kunjwa, Thulisile
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53642 , vital:45690
- Description: Passive seismic interferometry is a process by which ambient noise data recorded at different seismic stations can be cross-correlated to estimate Green's functions. In the past, both surface waves and body waves have successfully been extracted by cross-correlation of ambient noise data on both regional and global scales. Recent advancements in ambient seismic noise techniques have the potential to provide new methods for subsurface imaging and monitoring. The ambient noise data processing procedure divides into four principal phases: (1) single station data preparation, (2) cross-correlation and temporal stacking, (3) measurement of dispersion curves and (4) inversion of dispersion curves to obtain 1-D shear wave profiles and computation of 2-D shear wave velocity cross-section. The purpose of this study is to investigate whether ambient seismic noise can be used to image and detect internal changes within a mine tailings dam wall and to image the subsurface geology of part of the Eastern Cape Karoo near Cradock. In the first experiment, the investigation consisted of continuous ambient noise data recordings over a period of 3 days with 20 three-component short period geophones. The geophones were deployed over a survey wall of roughly 100 m in length at the Harmony Gold mine tailings dam in Welkom. In the second experiment, the investigation consisted of data recordings over a period of 35 days. The geophones were deployed in Cradock. The first phase of the data processing procedure included de-trending, de-meaning and band-pass filtering the data. This was done to ensure that any long period trends associated with instrument glitches are removed from the data. A spectrogram was then computed to view the spectrum of frequencies in the signal and to check if the filter that was designed was able to cut off the unwanted frequencies. The horizontal and vertical components of the ambient noise data were cross-correlated and picked between sensor pairs to create surface wave dispersion curves. Subsequently, the dispersion curves were inverted to estimate the shear wave velocity of the dam wall and subsurface as a function of depth. The computed cross sections of shear wave velocity indicated a low-velocity zone between 2 and 10 m below the surface on the dam wall, this suggested that the phreatic surface is much closer to surface in this area. In the second experiment, the interpolated shear wave velocity profiles indicated that there is a layer of low velocity zone between depths 250 to 300 m below the surface. The cross-correlations were also used to compute group velocity maps from periods 1.5 seconds to 30 seconds. The group velocity maps showed various high and low velocity anomalies. The high velocity zones observed on the eastern section of the map were interpreted as evidence of dolerite intrusions. The low velocity zones observed in the western and southern sections of the map interpreted as Karoo sediments that belong to the Adelaide Subgroup which is dominated by mudstones. , Thesis (MSc) -- Faculty of Science, Department of Geosciences (Geology and Geography), 2021
- Full Text:
- Date Issued: 2021-12
The use of a rapid incineration field test for determining soil organic carbon in the Southern Cape Region
- Authors: Ackhurst, Albert Arthur
- Date: 2014-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53336 , vital:45135
- Description: Knowledge of soil organic carbon levels is important both for agricultural effectiveness and soil carbon sequestration accounting, especially against the backdrop of increased climate change impacts and pressure on food production landscapes. However, current methods for soil carbon determination are expensive, energy intensive, time consuming and potentially hazardous leading to a call for alternative methods, which should be cheap, fast, simple, accurate, safe and usable where resources and soil analysis laboratories are limited. To this end the student invented a novel rapid incineration field test (RIFT) for determining soil organic carbon and tested its validity in this study. This method incorporates principles found in dry combustion as well as loss-on-ignition and quantifying organic carbon through gravimetric analysis. In order to illustrate effectiveness and accuracy it was necessary to correlate RIFT with a reference method, in this instance dry combustion with a Leco device as well as another commonly used indirect method namely the Walkley-Black wet chemical oxidation method. Samples from eleven soil forms were collected from the Southern Cape region and they were subjected to the three testing methods. It was found that RIFT is indeed as effective and in 72% of the soil forms even more effective than Walkley-Black. Furthermore, it was ascertained whether the accuracy of RIFT can be improved by correcting for clay content. The correlation of RIFT with clay % was not very significant and clay % as a variable was therefore not used in this study to obtain further refinement of RIFT predictions. Another finding was also that RIFT illustrated less variability than both the Leco and Walkley-Black methods. Lastly it was ascertained that the RIFT device and methodology is indeed cost effective, energy efficient, fast and safe in terms of the need to use potentially hazardous chemicals. , Thesis (MA) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text:
- Date Issued: 2014-12
- Authors: Ackhurst, Albert Arthur
- Date: 2014-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53336 , vital:45135
- Description: Knowledge of soil organic carbon levels is important both for agricultural effectiveness and soil carbon sequestration accounting, especially against the backdrop of increased climate change impacts and pressure on food production landscapes. However, current methods for soil carbon determination are expensive, energy intensive, time consuming and potentially hazardous leading to a call for alternative methods, which should be cheap, fast, simple, accurate, safe and usable where resources and soil analysis laboratories are limited. To this end the student invented a novel rapid incineration field test (RIFT) for determining soil organic carbon and tested its validity in this study. This method incorporates principles found in dry combustion as well as loss-on-ignition and quantifying organic carbon through gravimetric analysis. In order to illustrate effectiveness and accuracy it was necessary to correlate RIFT with a reference method, in this instance dry combustion with a Leco device as well as another commonly used indirect method namely the Walkley-Black wet chemical oxidation method. Samples from eleven soil forms were collected from the Southern Cape region and they were subjected to the three testing methods. It was found that RIFT is indeed as effective and in 72% of the soil forms even more effective than Walkley-Black. Furthermore, it was ascertained whether the accuracy of RIFT can be improved by correcting for clay content. The correlation of RIFT with clay % was not very significant and clay % as a variable was therefore not used in this study to obtain further refinement of RIFT predictions. Another finding was also that RIFT illustrated less variability than both the Leco and Walkley-Black methods. Lastly it was ascertained that the RIFT device and methodology is indeed cost effective, energy efficient, fast and safe in terms of the need to use potentially hazardous chemicals. , Thesis (MA) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text:
- Date Issued: 2014-12
The synthesis of anastrazole intermediates using continuous flow systems
- Authors: Tanyi, Sam Tambi
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54116 , vital:46304
- Description: In this study, the continuous flow synthesis of anastrozole intermediates were investigated using mesitylene as starting material. Anastrozole is an important drug used for the treatment of breast cancer. In the first step, mesitylene was brominated using N-bromosuccinimide to obtain 3,5-bis(bromomethyl)toluene. Selectivity became an issue due to the formation of two by-products; namely 1,3,5-tris(bromomethyl) benzene (the tribrominated by-product) and 1-(bromomethyl)-3,5-dimethylbenzene (the monobrominated by-product). Since the reaction parameters can be more precisely controlled in flow chemistry systems, we were able to optimize the formation the desired product 3,5-bis(bromomethyl)toluene. The reaction was initially optimized ina 15μLChemtrix glass micro reactor resulting in 100%conversion with 95%selectivity towards the desired product 3,5-bis(bromomethyl)toluenein 15 seconds, with a throughput of 0.006 g/h. The reaction was then scaled up in a 1.7 mLLTF reactor, equally yielding 100%conversion with 95%selectivityin 4minutes, with a throughput of2.01g/h. The bromination of mesitylene was also attempted in a homemade photochemical reactor consisting of a 3.02 polytetrafluoroethylene coil reactor and BLE-6T365 UV lamp. In this photochemical reactor, although 100%conversionwas again obtained only75%selectivity was achieved in 20minutes, with a throughput of 0.025g/h. This drop in selectivity was attributed to poorer mixing in the larger polytetrafluoroethylene coil reactor and possibly insufficient light penetration. The next step, involving the cyanation of 3,5-bis(bromomethyl)toluene to obtain 2,2'-(5-methyl-1,3-phenylene) diacetonitrilegave 100%conversion in 1 minute at 190 °C in a 1.7 mLLTFreactor, with a throughput of 5.2g/h. The subsequent methylation of 3,5-bis(cyanomethyl)toluene to obtain3,5-bis(1-cyano-1-methylethyl) toluene was investigated using a1mLpolytetrafluoroethylenecoil reactor, ultimatelyachieving99%conversionat40 °Cin 8minutes, with a throughput of 0.045g/h. Next, the bromination of3,5-bis(1-cyano-1-methylethyl)toluene using N-bromosuccinimideto yield 2,2'-(5-bromomethyl-1,3-phenylene)di(2-methyl propionitrile) gave 100%conversion at 120 °C in 4 minutes, with a throughput of 0.35g/h. Lastly, the multistep synthesis of 3,5-bis(cyanomethyl)toluene was done in two integrated 1.7 mLLTF reactors, using the predetermined optimum conditions to achieve 94%conversion towards 3,5-bis(cyanomethyl)toluene with a total r , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Tanyi, Sam Tambi
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54116 , vital:46304
- Description: In this study, the continuous flow synthesis of anastrozole intermediates were investigated using mesitylene as starting material. Anastrozole is an important drug used for the treatment of breast cancer. In the first step, mesitylene was brominated using N-bromosuccinimide to obtain 3,5-bis(bromomethyl)toluene. Selectivity became an issue due to the formation of two by-products; namely 1,3,5-tris(bromomethyl) benzene (the tribrominated by-product) and 1-(bromomethyl)-3,5-dimethylbenzene (the monobrominated by-product). Since the reaction parameters can be more precisely controlled in flow chemistry systems, we were able to optimize the formation the desired product 3,5-bis(bromomethyl)toluene. The reaction was initially optimized ina 15μLChemtrix glass micro reactor resulting in 100%conversion with 95%selectivity towards the desired product 3,5-bis(bromomethyl)toluenein 15 seconds, with a throughput of 0.006 g/h. The reaction was then scaled up in a 1.7 mLLTF reactor, equally yielding 100%conversion with 95%selectivityin 4minutes, with a throughput of2.01g/h. The bromination of mesitylene was also attempted in a homemade photochemical reactor consisting of a 3.02 polytetrafluoroethylene coil reactor and BLE-6T365 UV lamp. In this photochemical reactor, although 100%conversionwas again obtained only75%selectivity was achieved in 20minutes, with a throughput of 0.025g/h. This drop in selectivity was attributed to poorer mixing in the larger polytetrafluoroethylene coil reactor and possibly insufficient light penetration. The next step, involving the cyanation of 3,5-bis(bromomethyl)toluene to obtain 2,2'-(5-methyl-1,3-phenylene) diacetonitrilegave 100%conversion in 1 minute at 190 °C in a 1.7 mLLTFreactor, with a throughput of 5.2g/h. The subsequent methylation of 3,5-bis(cyanomethyl)toluene to obtain3,5-bis(1-cyano-1-methylethyl) toluene was investigated using a1mLpolytetrafluoroethylenecoil reactor, ultimatelyachieving99%conversionat40 °Cin 8minutes, with a throughput of 0.045g/h. Next, the bromination of3,5-bis(1-cyano-1-methylethyl)toluene using N-bromosuccinimideto yield 2,2'-(5-bromomethyl-1,3-phenylene)di(2-methyl propionitrile) gave 100%conversion at 120 °C in 4 minutes, with a throughput of 0.35g/h. Lastly, the multistep synthesis of 3,5-bis(cyanomethyl)toluene was done in two integrated 1.7 mLLTF reactors, using the predetermined optimum conditions to achieve 94%conversion towards 3,5-bis(cyanomethyl)toluene with a total r , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-12
The quantification of Pinus patula recovery and productivity of manually orientated biomass collection in post mechanised full tree and semi mechanised tree length harvesting operations
- Authors: Ncongwane, Thandekile Hazel
- Date: 2023-04
- Subjects: Pinus patula – south Africa , Forest ecology , Biomass energy
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61511 , vital:70692
- Description: The use of biomass as an alternate source of energy has grown in popularity. Different types of biomass are obtained from a variety of sources including natural forests, forestry plantations and agriculture residues. However, forestry residues have been identified as the most promising source, due to the wide variety of plant products including leaves, twigs, branches, merchantable stem, stumps and roots. The main sources of plantation forest biomass are residues from thinning, clearfell and conventional products such as pulpwood and sawn timber operations. These residues can accumulate between 4.3 to 9.4 billion tonnes annually around the world. The biomass availability in plantation forests has led to the development of different harvesting systems to help collect the products from infield to sawmill. Biomass harvesting has mainly been achieved through mechanised systems because of their high yields. However, the use of manual systems has been neglected due to technical limitations and financial viability. Thus, in South Africa, there is no scientific research looking at manual systems of collecting biomass from plantations. Because of this, different forestry stakeholders, including small growers and contractors using manual systems for biomass harvesting have limited knowledge regarding what to expect in terms of recoverable amounts, productivity and cost. This research examines the productivity of the manual biomass collection and the quantification of recovered and unrecovered residues after mechanised full tree (FT) and semi mechanised tree length (TL) harvesting operations in Pinus patula compartments. A total number of 8 plots with +/-200 standing trees were marked in each system. The diameter and height of all marked trees were measured to determine tree volume. Moreover, the quantification of recoverable woody biomass was determined, where after, a residues assessment method using plots and line transects was used to determine the amount of unrecovered residues. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Ncongwane, Thandekile Hazel
- Date: 2023-04
- Subjects: Pinus patula – south Africa , Forest ecology , Biomass energy
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61511 , vital:70692
- Description: The use of biomass as an alternate source of energy has grown in popularity. Different types of biomass are obtained from a variety of sources including natural forests, forestry plantations and agriculture residues. However, forestry residues have been identified as the most promising source, due to the wide variety of plant products including leaves, twigs, branches, merchantable stem, stumps and roots. The main sources of plantation forest biomass are residues from thinning, clearfell and conventional products such as pulpwood and sawn timber operations. These residues can accumulate between 4.3 to 9.4 billion tonnes annually around the world. The biomass availability in plantation forests has led to the development of different harvesting systems to help collect the products from infield to sawmill. Biomass harvesting has mainly been achieved through mechanised systems because of their high yields. However, the use of manual systems has been neglected due to technical limitations and financial viability. Thus, in South Africa, there is no scientific research looking at manual systems of collecting biomass from plantations. Because of this, different forestry stakeholders, including small growers and contractors using manual systems for biomass harvesting have limited knowledge regarding what to expect in terms of recoverable amounts, productivity and cost. This research examines the productivity of the manual biomass collection and the quantification of recovered and unrecovered residues after mechanised full tree (FT) and semi mechanised tree length (TL) harvesting operations in Pinus patula compartments. A total number of 8 plots with +/-200 standing trees were marked in each system. The diameter and height of all marked trees were measured to determine tree volume. Moreover, the quantification of recoverable woody biomass was determined, where after, a residues assessment method using plots and line transects was used to determine the amount of unrecovered residues. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
The potential impacts of hydraulic fracturing on Khoisan peoples’ sense of place: in the case of Karoo Region, South Africa
- Authors: Tembe, Thandeka
- Date: 2022-04
- Subjects: Hydraulic fracturing--Environmental aspects--South Africa--Eastern Cape , Khoikhoi (African people) -- History
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55701 , vital:53408
- Description: Hydraulic fracturing is a practical solution to minimising production of fossil fuels and to boost the South African economy. However, this development comes at a cost to the society, environment and heritage of the Karoo, which is home to majority of the Khoisan community. Developments such as hydraulic fracturing are barely understood by local communities therefore this study tried to determine the potential impacts of hydraulic fracturing on Khoisan people’s sense of place in the Karoo region, to also establish their perceptions, attitudes, opinion and knowledge on hydraulic fracturing, to facilitate and improve understanding. A mixed method approach was employed to gather relevant information from participants. The qualitative data collection used semi structured interviews to gain participants perceptions, attitudes, opinions and knowledge on hydraulic fracturing, whereas quantitative used questionnaire survey which was administrated to gain socio-demographics and sense of place of Khoisan people (N=50) using survey based psychometric approach to examine the relationship between Khoisan people and sense of place on proposed hydraulic fracturing in the Karoo region (Cradock). Primary data was employed to gain in depth raw data directly from participants and secondary data from literature that already exists. The purposive and snowball sampling technique was used to draw Khoisan participants from the Karoo region (Cradock). Data acquired was analysed using SPSS v26 and Microsoft excel. The results concluded that most Khoisan participants (N= 43) are not aware of what hydraulic fracturing is and therefore there is a need to be taught about the development. The (N= 7) of the participants who have an idea of what hydraulic fracturing is had attended a workshop that was facilitated by the AEON research institute, others learnt about it on the internet and others were informed by someone who either learnt from the internet or attend the workshop. The study also concluded that the Khoisan people have a strong positive sense of place (α= 0.922) with the Karoo region therefore going ahead with the proposed hydraulic fracturing will cause massive damage and could possibly lead to solastalgia and loss of sense of place. vi The recommendation of the study was to involve all stakeholders who will be part of the development of hydraulic fracturing from government, research institutes to oil and gas companies to thorough research, educate and inform local communities in the Karoo. Therefore, it is essential for the government to protect the Karoo culture and heritage, local peoples sense of place by communicating with local communities on such development and assist in holding these companies reliable for any misconducts. , Thesis (MSc) -- Faculty of Science, Environmental Geography, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Tembe, Thandeka
- Date: 2022-04
- Subjects: Hydraulic fracturing--Environmental aspects--South Africa--Eastern Cape , Khoikhoi (African people) -- History
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55701 , vital:53408
- Description: Hydraulic fracturing is a practical solution to minimising production of fossil fuels and to boost the South African economy. However, this development comes at a cost to the society, environment and heritage of the Karoo, which is home to majority of the Khoisan community. Developments such as hydraulic fracturing are barely understood by local communities therefore this study tried to determine the potential impacts of hydraulic fracturing on Khoisan people’s sense of place in the Karoo region, to also establish their perceptions, attitudes, opinion and knowledge on hydraulic fracturing, to facilitate and improve understanding. A mixed method approach was employed to gather relevant information from participants. The qualitative data collection used semi structured interviews to gain participants perceptions, attitudes, opinions and knowledge on hydraulic fracturing, whereas quantitative used questionnaire survey which was administrated to gain socio-demographics and sense of place of Khoisan people (N=50) using survey based psychometric approach to examine the relationship between Khoisan people and sense of place on proposed hydraulic fracturing in the Karoo region (Cradock). Primary data was employed to gain in depth raw data directly from participants and secondary data from literature that already exists. The purposive and snowball sampling technique was used to draw Khoisan participants from the Karoo region (Cradock). Data acquired was analysed using SPSS v26 and Microsoft excel. The results concluded that most Khoisan participants (N= 43) are not aware of what hydraulic fracturing is and therefore there is a need to be taught about the development. The (N= 7) of the participants who have an idea of what hydraulic fracturing is had attended a workshop that was facilitated by the AEON research institute, others learnt about it on the internet and others were informed by someone who either learnt from the internet or attend the workshop. The study also concluded that the Khoisan people have a strong positive sense of place (α= 0.922) with the Karoo region therefore going ahead with the proposed hydraulic fracturing will cause massive damage and could possibly lead to solastalgia and loss of sense of place. vi The recommendation of the study was to involve all stakeholders who will be part of the development of hydraulic fracturing from government, research institutes to oil and gas companies to thorough research, educate and inform local communities in the Karoo. Therefore, it is essential for the government to protect the Karoo culture and heritage, local peoples sense of place by communicating with local communities on such development and assist in holding these companies reliable for any misconducts. , Thesis (MSc) -- Faculty of Science, Environmental Geography, 2022
- Full Text:
- Date Issued: 2022-04
The influence of site characteristics on growth and wood properties of Pinus radiata and Pinus elliottii in the Southern and Eastern Cape forestry regions of South Africa
- Authors: Sigcau, Chulumanco
- Date: 2023-04
- Subjects: Forests and forestry -- Environmental aspects , Pine – Growth -- South Africa , Pinus radiata
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61234 , vital:69828
- Description: The intensive nature of plantation forestry in South Africa requires efficiency and financial viability in production systems, amidst a complex growing environment subjected to changing macro-climatic patterns. The success of plantation forestry operations depends, amongst others, on our understanding of tree growth and wood formation patterns in response to variable growing conditions in both space and time. This study was conducted on the two most commonly used species in the southern and Eastern Cape forestry regions, i.e., Pinus radiata and P. elliottii. The region is regarded as highly suitable for plantation forestry in terms of climatic conditions, but soil characteristics pose several challenges due to nutritional disorders and poor drainage. The study focused on investigating the influence of both soil and climatic conditions on the growth and Wood Density properties of the two species, and to establish functional relationships where possible. The two species showed comparable growth rates at the reference age of 13 years on the range of sites sampled in the study area. An analysis of variance showed greater differences in Site Index between than within sample plots, pointing towards the possible influence of site on growth variation. Correlations between climatic variables and the growth of both species were generally weak and contradictory. Possible reasons for this phenomenon are discussed. It is proposed that the general favourable climatic profile of the region and hydromorphic nature of soils reduce the chances of significant correlations between variables influencing moisture availability and tree growth. The analysis of correlations between soil parameters and tree growth revealed some influence of soil organic C and Na on the growth of P. elliottii. This is discussed in terms of our understanding of the influence of soil parent material and soil ecology. The absence of any correlations between soil chemical parameters and the growth of P. radiata was conspicuous. This is in contradiction with earlier studies on the species in the region and can possibly be explained in terms of the site-specific fertilizing policy of the industry, as well as the less diverse range of sites sampled than in the past, which can mask or reduce nutrient limitations for tree growth. However, P. radiata did show a high level of sensitivity towards effective soil depth. Site-quality prediction models are proposed for the two species, but with variable application value due to the limited options of significant control variables that can be considered for inclusion in the models. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science and Management, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Sigcau, Chulumanco
- Date: 2023-04
- Subjects: Forests and forestry -- Environmental aspects , Pine – Growth -- South Africa , Pinus radiata
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61234 , vital:69828
- Description: The intensive nature of plantation forestry in South Africa requires efficiency and financial viability in production systems, amidst a complex growing environment subjected to changing macro-climatic patterns. The success of plantation forestry operations depends, amongst others, on our understanding of tree growth and wood formation patterns in response to variable growing conditions in both space and time. This study was conducted on the two most commonly used species in the southern and Eastern Cape forestry regions, i.e., Pinus radiata and P. elliottii. The region is regarded as highly suitable for plantation forestry in terms of climatic conditions, but soil characteristics pose several challenges due to nutritional disorders and poor drainage. The study focused on investigating the influence of both soil and climatic conditions on the growth and Wood Density properties of the two species, and to establish functional relationships where possible. The two species showed comparable growth rates at the reference age of 13 years on the range of sites sampled in the study area. An analysis of variance showed greater differences in Site Index between than within sample plots, pointing towards the possible influence of site on growth variation. Correlations between climatic variables and the growth of both species were generally weak and contradictory. Possible reasons for this phenomenon are discussed. It is proposed that the general favourable climatic profile of the region and hydromorphic nature of soils reduce the chances of significant correlations between variables influencing moisture availability and tree growth. The analysis of correlations between soil parameters and tree growth revealed some influence of soil organic C and Na on the growth of P. elliottii. This is discussed in terms of our understanding of the influence of soil parent material and soil ecology. The absence of any correlations between soil chemical parameters and the growth of P. radiata was conspicuous. This is in contradiction with earlier studies on the species in the region and can possibly be explained in terms of the site-specific fertilizing policy of the industry, as well as the less diverse range of sites sampled than in the past, which can mask or reduce nutrient limitations for tree growth. However, P. radiata did show a high level of sensitivity towards effective soil depth. Site-quality prediction models are proposed for the two species, but with variable application value due to the limited options of significant control variables that can be considered for inclusion in the models. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science and Management, 2023
- Full Text:
- Date Issued: 2023-04
The impact of transformed landscapes on the resource selection and occupancy of specialized browsing species in a lowland fynbos and renosterveld ecosystem
- Swanepoel, Hermanus Izak Johannes
- Authors: Swanepoel, Hermanus Izak Johannes
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54132 , vital:46308
- Description: Human activities have dramatically transformed the natural environment over the last century. In most cases these activities have resulted in the destruction and fragmentation of habitats. However, in some areas the transformation of landscapes through agriculture have created novel habitats which could benefit some species. The effect of these transformed landscapes on the resource selection and occupancy of antelope species in different vegetation types such as fynbos and renosterveld are still understudied. In order to investigate this,we conducted a study in the Overberg region of the Western Cape, South Africa. We studied theoccupancy and habitat useof five specialist browsing species (Tragelaphus scriptus sylvaticus(bushbuck), Rhaphicerus melanotis(cape grysbok), Sylvicapra grimmia(common duiker), Palea Capreolus(grey rhebok) and Rhaphicerus campestris(steenbok)) within a transformed landscape. We collected speciesdetection/ non-detectionand presence/ absence data using camera traps and road strip counts.Usinga single season, single species occupancy framework as a surrogate for habitat usewedeterminedhow transformed landscapes affected their occupancy. Using aniche factor analysis and resource selection functions wedetermine how transformed landscapes affected the resource selectionof these species. Our results from the resource selection analysis indicated that steenbok, grey rhebok, andcommon duiker included crops such as wheat and planted pastures in their resource selection while also including natural vegetation. Cape grysbok and bushbuck selected predominantly for natural vegetation areas such as critical biodiversity areas and ecological support areas while also including some crops in their resource selection. Our results from the occupancy analysis indicatedthat steenbok, grey rhebok and common duiker had a higher occupancy in the transformed landscape than in the natural landscape. Bushbuck and Cape grysbok showed little to no difference in their occupancy between land use types. The insight provided by our results will allow practitioners to maximise the potentialof these mosaic landscape in the Overberg for mammal conservation.The study also provides a baseline from which further research and monitoring programs can be developed to further understand the dynamics of this landscape. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Swanepoel, Hermanus Izak Johannes
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54132 , vital:46308
- Description: Human activities have dramatically transformed the natural environment over the last century. In most cases these activities have resulted in the destruction and fragmentation of habitats. However, in some areas the transformation of landscapes through agriculture have created novel habitats which could benefit some species. The effect of these transformed landscapes on the resource selection and occupancy of antelope species in different vegetation types such as fynbos and renosterveld are still understudied. In order to investigate this,we conducted a study in the Overberg region of the Western Cape, South Africa. We studied theoccupancy and habitat useof five specialist browsing species (Tragelaphus scriptus sylvaticus(bushbuck), Rhaphicerus melanotis(cape grysbok), Sylvicapra grimmia(common duiker), Palea Capreolus(grey rhebok) and Rhaphicerus campestris(steenbok)) within a transformed landscape. We collected speciesdetection/ non-detectionand presence/ absence data using camera traps and road strip counts.Usinga single season, single species occupancy framework as a surrogate for habitat usewedeterminedhow transformed landscapes affected their occupancy. Using aniche factor analysis and resource selection functions wedetermine how transformed landscapes affected the resource selectionof these species. Our results from the resource selection analysis indicated that steenbok, grey rhebok, andcommon duiker included crops such as wheat and planted pastures in their resource selection while also including natural vegetation. Cape grysbok and bushbuck selected predominantly for natural vegetation areas such as critical biodiversity areas and ecological support areas while also including some crops in their resource selection. Our results from the occupancy analysis indicatedthat steenbok, grey rhebok and common duiker had a higher occupancy in the transformed landscape than in the natural landscape. Bushbuck and Cape grysbok showed little to no difference in their occupancy between land use types. The insight provided by our results will allow practitioners to maximise the potentialof these mosaic landscape in the Overberg for mammal conservation.The study also provides a baseline from which further research and monitoring programs can be developed to further understand the dynamics of this landscape. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text:
- Date Issued: 2021-12
The Impact of socio-Economic and institutional factors on the Livelihoods of artisanal fisherfolk of Korsten, Gqeberha.
- Authors: Forbes-Liberty,Abigail
- Date: 2022-04
- Subjects: Fishing--Social aspects -- South Africa , Korsten-- Gqeberha
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55584 , vital:53334
- Description: his dissertation focuses on a relatively underrepresented group of the fishing industry: subsistence fisherfolk. By using a Sustainable Livelihoods Approach (SLA) and Community Capitals Framework (CCF) as a theoretical framework and interpretive lens, the purpose of this qualitative study is to explore the impact of socio-economic and institutional factors on the livelihoods of artisanal fisherfolk of Korsten, Gqeberha (formerly known as Port Elizabeth). By highlighting the socio-spatial implications of the forced removals of the past, this dissertation shows that legislative reforms should consider the population that they affect. Food security is a major issue on a global scale and South Africa is not impervious to food security concerns. This dissertation focuses on the negative impact that socio-economic climate and legislation has had on subsistence fisherfolk. Hunger and poverty eradication is one of the key goals of sustainable development. In this case, subsistence fishers faced legislative reforms at two distinct points in its tumultuous past, both of which had a detrimental impact on this sector of society's ability to support a healthy livelihood. This research fills a theoretical and practical gap in research regarding the current livelihoods, policies, and laws, as well as provides a deeper understanding of the socio-economic context of the subsistence fishing community of Korsten, Gqeberha. The SLA and CCF helps readers understand how subsistence fishers contribute to local livelihoods and integrate into the greater processes of the community. Further, exploration of the institutional policies limiting subsistence fishers helps understand decision making processes and laws in artisanal fisheries and the implications thereof. A snowball sampling method was used to recruit and enrol participants for this study. The sample size consisted of fourteen (14) participants consisting of eight (8) subsistence fishers and six (6) relatives of subsistence fisherfolk. Narrative analysis is a qualitative method that was conducted in this study. Participant observation and semi-structured interviews were conducted as the methods of data collection and analysed in ATLAS.ti 9 Qualitative Analysis Software. Most participants indicated that fishing plays an integral part of their lives. It contributes to and still ensures the food security in the families of Korsten. In addition, participants highlighted the constant legislative and socio-economic barriers as well as the social and personal benefits of fishing in the community. A key recommendation is made for policy-makers to be cognizant of subsistence fishers and to include this underrepresented group in decision making processes. , Thesis (MSc) -- Faculty of Science, Geosciences, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Forbes-Liberty,Abigail
- Date: 2022-04
- Subjects: Fishing--Social aspects -- South Africa , Korsten-- Gqeberha
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55584 , vital:53334
- Description: his dissertation focuses on a relatively underrepresented group of the fishing industry: subsistence fisherfolk. By using a Sustainable Livelihoods Approach (SLA) and Community Capitals Framework (CCF) as a theoretical framework and interpretive lens, the purpose of this qualitative study is to explore the impact of socio-economic and institutional factors on the livelihoods of artisanal fisherfolk of Korsten, Gqeberha (formerly known as Port Elizabeth). By highlighting the socio-spatial implications of the forced removals of the past, this dissertation shows that legislative reforms should consider the population that they affect. Food security is a major issue on a global scale and South Africa is not impervious to food security concerns. This dissertation focuses on the negative impact that socio-economic climate and legislation has had on subsistence fisherfolk. Hunger and poverty eradication is one of the key goals of sustainable development. In this case, subsistence fishers faced legislative reforms at two distinct points in its tumultuous past, both of which had a detrimental impact on this sector of society's ability to support a healthy livelihood. This research fills a theoretical and practical gap in research regarding the current livelihoods, policies, and laws, as well as provides a deeper understanding of the socio-economic context of the subsistence fishing community of Korsten, Gqeberha. The SLA and CCF helps readers understand how subsistence fishers contribute to local livelihoods and integrate into the greater processes of the community. Further, exploration of the institutional policies limiting subsistence fishers helps understand decision making processes and laws in artisanal fisheries and the implications thereof. A snowball sampling method was used to recruit and enrol participants for this study. The sample size consisted of fourteen (14) participants consisting of eight (8) subsistence fishers and six (6) relatives of subsistence fisherfolk. Narrative analysis is a qualitative method that was conducted in this study. Participant observation and semi-structured interviews were conducted as the methods of data collection and analysed in ATLAS.ti 9 Qualitative Analysis Software. Most participants indicated that fishing plays an integral part of their lives. It contributes to and still ensures the food security in the families of Korsten. In addition, participants highlighted the constant legislative and socio-economic barriers as well as the social and personal benefits of fishing in the community. A key recommendation is made for policy-makers to be cognizant of subsistence fishers and to include this underrepresented group in decision making processes. , Thesis (MSc) -- Faculty of Science, Geosciences, 2022
- Full Text:
- Date Issued: 2022-04
The feeding ecology and habitat selection of small antelopes in the Overberg Renosterveld, Western Cape
- Authors: Jansen van Vuuren, Amauréé
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Fynbos ecology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52014 , vital:43436
- Description: Human impacts have altered natural ecosystems which required species to become resilient in order to survive the anthropogenic landscape. The study area is located in the highly fragmented Overberg area in the Western Cape of South Africa. The high degree of fragmentation of the area is as a result of the nutrient rich soils and favourable topography which makes the area highly suitable for agricultural practices. The agriculture practiced in the area is mainly grain crops and livestock farming and the remaining patches of natural vegetation consist of Fynbos and Renosterveld vegetation. The patches of Fynbos and Renosterveld vegetation acts as movement corridors to allow species movement through the anthropogenic landscape. The anthropogenic landscape requires species to be resilient and to adapt to a novel habitat which poses new threats as well as new resources. The aim of the study is to investigate the effect of landscape transformation, resulting from agricultural practices, on the feeding and behavioural dynamics of five small specialist browser species in a fragmented lowland Fynbos and Renosterveld system. The objectives were to determine the forage preferences of each of the five specialist browser species and to determine which site-specific characteristics, drive the seasonal habitat use of the five specialist browser species. The five specialist browser species were bushbuck (Tragelaphus sylvaticus), Cape grysbok (Rhaphicerus melanotis), common duiker (Sylvicapra grimmia), grey rhebok (Pelea capreolus) and steenbok (Rhaphicerus campestris). To determine the dietary selection of the five specialist browser species we collected dung samples and performed a histological analysis on the dung samples. To determine the habitat use of the five specialist browser species we used an occupancy analysis framework on camera trap data collected on each of the species. Some species appeared more dependent on the food resources from the anthropogenic landscape and spent more time in the crops but required close by cover of natural vegetation. Others appeared more dependent on the remaining pockets of natural vegetation for food resources and spent more time in the natural vegetation. These species would occasionally move into the crops to utilise the food resources. Both the anthropogenic as well as the natural landscape contributed to the diets of all of the species. These species have been resilient to changes in the landscape and appear to be benefiting from the resources presented in the novel landscape. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Jansen van Vuuren, Amauréé
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Fynbos ecology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52014 , vital:43436
- Description: Human impacts have altered natural ecosystems which required species to become resilient in order to survive the anthropogenic landscape. The study area is located in the highly fragmented Overberg area in the Western Cape of South Africa. The high degree of fragmentation of the area is as a result of the nutrient rich soils and favourable topography which makes the area highly suitable for agricultural practices. The agriculture practiced in the area is mainly grain crops and livestock farming and the remaining patches of natural vegetation consist of Fynbos and Renosterveld vegetation. The patches of Fynbos and Renosterveld vegetation acts as movement corridors to allow species movement through the anthropogenic landscape. The anthropogenic landscape requires species to be resilient and to adapt to a novel habitat which poses new threats as well as new resources. The aim of the study is to investigate the effect of landscape transformation, resulting from agricultural practices, on the feeding and behavioural dynamics of five small specialist browser species in a fragmented lowland Fynbos and Renosterveld system. The objectives were to determine the forage preferences of each of the five specialist browser species and to determine which site-specific characteristics, drive the seasonal habitat use of the five specialist browser species. The five specialist browser species were bushbuck (Tragelaphus sylvaticus), Cape grysbok (Rhaphicerus melanotis), common duiker (Sylvicapra grimmia), grey rhebok (Pelea capreolus) and steenbok (Rhaphicerus campestris). To determine the dietary selection of the five specialist browser species we collected dung samples and performed a histological analysis on the dung samples. To determine the habitat use of the five specialist browser species we used an occupancy analysis framework on camera trap data collected on each of the species. Some species appeared more dependent on the food resources from the anthropogenic landscape and spent more time in the crops but required close by cover of natural vegetation. Others appeared more dependent on the remaining pockets of natural vegetation for food resources and spent more time in the natural vegetation. These species would occasionally move into the crops to utilise the food resources. Both the anthropogenic as well as the natural landscape contributed to the diets of all of the species. These species have been resilient to changes in the landscape and appear to be benefiting from the resources presented in the novel landscape. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text: false
- Date Issued: 2021-04
The effect of limestone ammonium nitrate and chicken manure fertilizers on growth, yield and quality of two cabbage cultivators
- Authors: Nongogo Chumani
- Date: 2022-12
- Subjects: Cabbage -- South Africa , Field crops -- Nutrition -- South Africa , fertilizers
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59922 , vital:62695
- Description: Cabbage is a well-known and popular crop in South Africa. As a highly nutritious leafy green vegetable, it is produced and sold to a variety of markets, from formal markets to hawkers, for human consumption and as animal feed. The cabbage crop contributes positively to food security, health, and households’ financial wellbeing. As a crop, cabbage is known to be a heavy feeder due to its high nutritional requirements (in terms of fertiliser) particularly nitrogen. This high requirement can be supplied by either synthetic or by organic fertilisers in the form of animal manures. However, fertiliser has proven to be a challenge due to its high costs, as its prices increase rapidly each year. The current study aimed to determine the most effective fertilisation method for the growth, quality, and yield of cabbage (Brassica oleracea var. capitata). Two fertiliser types (chicken manure and limestone ammonium nitrate) were applied, and the treatments were repeated five times over two planting sessions on two cultivars, Grandslam and Empowa, at concentrations of 0%, 100% and 150%. A control for each treatment / cultivar was also grown. The parameters plant height, head diameter, pests and disease development, quality and dry mass were measured to determine the effect on growth, yield, and quality of the cabbage crop. From each planting, a total of 60 cabbages served as specimens for data collection purposes. The research trial was conducted in open field and laid out in a split-plot block method. The cultivar was allocated to the main plot, while the fertiliser treatments served as the sub-plots. The study was carried out for a period of six months, which allowed for data collection to be done in two different growing conditions. Planting was done manually by hand in planting bags, and washed river sand was used as a substrate (growing medium). The data collected during the experiment was analysed by means of statistical data analysis software STATISTICA and the methods applied were a three-way analysis of variance (ANOVA). The analysis of variance was performed at a significance level of p as a means to determine a correlation of relationships for all set parameters (variables) for both cultivars, treatments and plantings. The results of the study showed that the two fertiliser types, namely limestone ammonium nitrate (LAN) and chicken manure, both had a significant effect (p on plant height, head diameter, dry mass. Also, the pest and disease development and quality of cabbage were significantly influenced by the fertiliser types and season (climate). The interactive effect of cultivar and fertiliser was statistically significant. Empowa showed better results on chicken manure compared to LAN. In the case of Grandslam, however, no significant fertiliser effect was observed. The study also showed that fertilisation with a fertiliser that contains high nitrogen (N) content promotes pest and disease incidence. Increasing N application rate resulted into an increase of pest and disease incidence. The change of season, which promotes different growth conditions (in terms of temperature, water requirements, pests, and diseases) for the plants was found to have had an influence on the study results. Lasty, it was observed that chicken manure fertiliser yields a cabbage with a good internal and external quality compared to limestone ammonium nitrate fertiliser. Lastly, when considering all treatment rates applied, the recommended quantity of 100% (in both chicken manure and LAN) yielded favorable results. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Nongogo Chumani
- Date: 2022-12
- Subjects: Cabbage -- South Africa , Field crops -- Nutrition -- South Africa , fertilizers
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59922 , vital:62695
- Description: Cabbage is a well-known and popular crop in South Africa. As a highly nutritious leafy green vegetable, it is produced and sold to a variety of markets, from formal markets to hawkers, for human consumption and as animal feed. The cabbage crop contributes positively to food security, health, and households’ financial wellbeing. As a crop, cabbage is known to be a heavy feeder due to its high nutritional requirements (in terms of fertiliser) particularly nitrogen. This high requirement can be supplied by either synthetic or by organic fertilisers in the form of animal manures. However, fertiliser has proven to be a challenge due to its high costs, as its prices increase rapidly each year. The current study aimed to determine the most effective fertilisation method for the growth, quality, and yield of cabbage (Brassica oleracea var. capitata). Two fertiliser types (chicken manure and limestone ammonium nitrate) were applied, and the treatments were repeated five times over two planting sessions on two cultivars, Grandslam and Empowa, at concentrations of 0%, 100% and 150%. A control for each treatment / cultivar was also grown. The parameters plant height, head diameter, pests and disease development, quality and dry mass were measured to determine the effect on growth, yield, and quality of the cabbage crop. From each planting, a total of 60 cabbages served as specimens for data collection purposes. The research trial was conducted in open field and laid out in a split-plot block method. The cultivar was allocated to the main plot, while the fertiliser treatments served as the sub-plots. The study was carried out for a period of six months, which allowed for data collection to be done in two different growing conditions. Planting was done manually by hand in planting bags, and washed river sand was used as a substrate (growing medium). The data collected during the experiment was analysed by means of statistical data analysis software STATISTICA and the methods applied were a three-way analysis of variance (ANOVA). The analysis of variance was performed at a significance level of p as a means to determine a correlation of relationships for all set parameters (variables) for both cultivars, treatments and plantings. The results of the study showed that the two fertiliser types, namely limestone ammonium nitrate (LAN) and chicken manure, both had a significant effect (p on plant height, head diameter, dry mass. Also, the pest and disease development and quality of cabbage were significantly influenced by the fertiliser types and season (climate). The interactive effect of cultivar and fertiliser was statistically significant. Empowa showed better results on chicken manure compared to LAN. In the case of Grandslam, however, no significant fertiliser effect was observed. The study also showed that fertilisation with a fertiliser that contains high nitrogen (N) content promotes pest and disease incidence. Increasing N application rate resulted into an increase of pest and disease incidence. The change of season, which promotes different growth conditions (in terms of temperature, water requirements, pests, and diseases) for the plants was found to have had an influence on the study results. Lasty, it was observed that chicken manure fertiliser yields a cabbage with a good internal and external quality compared to limestone ammonium nitrate fertiliser. Lastly, when considering all treatment rates applied, the recommended quantity of 100% (in both chicken manure and LAN) yielded favorable results. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
The effect of laundering on the physical and thermal properties of phase change textile materials
- Authors: Scheepers, Ricardo
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Textile chemistry
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52038 , vital:43443
- Description: Phase change materials (PCMs) have been incorporated into clothing and textiles to provide added value in terms of thermoregulation and thus added comfort to the wearer in extreme weather conditions and sporting activities. Since clothing is laundered many times during the service life of the textile, the effects of simulated domestic laundering on the physical and thermal properties of a non-woven textile which contains PCMs were investigated. The thermal properties, such as the thermal degradation, melting, evaporation and crystallisation were measured by the TGA and DSC analytical techniques. The physical properties, such as the microcapsule size distribution, and the microcapsule morphologies of the PCM microcapsules, were measured by the SEM and Raman analytical techniques. The main objectives of this study were to determine the effect of repeated laundering at different wash temperatures on the mass loss, enthalpy, and physical changes in PCM. Thermal degradation as determined by TGA thermograms was found to be higher at a wash temperature of 60°C relative to that of a wash temperature at 30°C, the mass loss being 4.6% more at 60°C than at 30°C. This was asserted to physical changes such as size and shape of the PCM microcapsules as evident in SEM images. The SEM images showed broken and collapsed PCM microcapsules in the web and around the fibre, indicating evaporation of the thermoregulating content of the PCM. It was found that the heat capacity of the sample washed at 60°C was much lower than that of the unwashed sample, the difference being approximately 50% in terms of the latent heat capacity as determined by DSC thermograms. This implies that the latent heat effectiveness of the PCM has decreased significantly. The physical properties of the PCM such as the intermolecular interaction, the intensity and width of peaks, polarisation, degree of crystallinity and the orientation changed as illustrated in the Raman analysis. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Scheepers, Ricardo
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Textile chemistry
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52038 , vital:43443
- Description: Phase change materials (PCMs) have been incorporated into clothing and textiles to provide added value in terms of thermoregulation and thus added comfort to the wearer in extreme weather conditions and sporting activities. Since clothing is laundered many times during the service life of the textile, the effects of simulated domestic laundering on the physical and thermal properties of a non-woven textile which contains PCMs were investigated. The thermal properties, such as the thermal degradation, melting, evaporation and crystallisation were measured by the TGA and DSC analytical techniques. The physical properties, such as the microcapsule size distribution, and the microcapsule morphologies of the PCM microcapsules, were measured by the SEM and Raman analytical techniques. The main objectives of this study were to determine the effect of repeated laundering at different wash temperatures on the mass loss, enthalpy, and physical changes in PCM. Thermal degradation as determined by TGA thermograms was found to be higher at a wash temperature of 60°C relative to that of a wash temperature at 30°C, the mass loss being 4.6% more at 60°C than at 30°C. This was asserted to physical changes such as size and shape of the PCM microcapsules as evident in SEM images. The SEM images showed broken and collapsed PCM microcapsules in the web and around the fibre, indicating evaporation of the thermoregulating content of the PCM. It was found that the heat capacity of the sample washed at 60°C was much lower than that of the unwashed sample, the difference being approximately 50% in terms of the latent heat capacity as determined by DSC thermograms. This implies that the latent heat effectiveness of the PCM has decreased significantly. The physical properties of the PCM such as the intermolecular interaction, the intensity and width of peaks, polarisation, degree of crystallinity and the orientation changed as illustrated in the Raman analysis. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
The development of a flow route to synthesize 3- benzyl-6-bromo-2-methoxyquinoline, an intermediate of an anti-TB drug, bedaquilin
- Authors: Mpalala, Anele
- Date: 2022-12
- Subjects: Multidrug-resistant tuberculosis -- South Africa , Tuberculosis --Chemotherapy -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59864 , vital:62455
- Description: SA has a high number of reported cases of multidrug-resistant tuberculosis (MDR-TB). Bedaquiline is a newly approved active ingredient of an anti-tuberculosis drug with high potency against MDR-TB. The limited access to this life-saving medicine to many people in the world has driven a great deal of research effort by the scientific community to find new, better and more practical approaches to this drug. However, many of the reported synthetic procedures suffer from long reaction times, which in turn require many hours of effort by the chemists conducting the reactions. This has prompted us to investigate an efficient process towards the synthesis to produce the key intermediates of bedaquiline using continuous flow technology. Additionally, since there is not much literature on continuous flow synthesis of bedaquiline, this research revealed interesting continuous flow processes towards the drug. Chapter 1: In order to provide insight, the first chapter of this dissertation presents a comprehensive background and literature review on tuberculosis; its pathogenesis, impact, medicines available for the treatment as well as the drug classes with novel mode of action and new chemical entities. Furthermore, bedaquiline is discussed in detail with the various synthetic protocols of the drug. An introduction to continuous flow chemistry is discussed, along with an outline of its advantages and disadvantages. Chapter 2: The second chapter encompasses the experimental procedures utilized for both batch and continuous flow syntheses. The three key intermediates of bedaquiline were synthesized in batch synthesis and these compounds were characterized using 1H-NMR, 13C-NMR and FT-IR spectroscopy. Subsequently, the continuous flow synthesis protocols for the preparations of these intermediates and their optimization are outlined. Chapter 3: The results are explained in this chapter with detailed discussions of the batch synthesis and the continuous flow optimization of each step within the scope of this research. The investigation started with the batch preparation of the primary intermediate, N-(4-bromophenyl)-3-phenylpropanamide via an amidation reaction between 3-phenylpropanoyl chloride and p-bromoaniline. The primary intermediate then undergoes a subsequent formylation and cyclization via a Vilsmeier–Haack reaction to yield 3-benzyl-6-bromo-2-chloroquinoline. The chloroquinoline ii intermediate undergoes a methoxylation reaction to form 3-benzyl-6-bromo-2- methoxyquinoline. Subsequently, the batch protocol was transferred into continuous flow systems, optimized by varying reaction parameters within the synthesis route to achieve the as much yield as possible. The optimization studies showed an improvement in conversions in the various steps with shorter reaction times. The first step was optimized in a 0.2ml microreactor and because of the enhanced safety of flow chemistry, this exothermic amidation reaction was optimised at elevated temperatures to afford the primary intermediate at a 100% conversion within a residence time of 5 seconds using DMF as a solvent with DIPEA as a base. Next, the Vilsmier-Haack cyclization and chlorination was optimised in flow to afford the 2-chloroquinoline intermediate. The ability to use a back pressure regulator allowed for investigation of the effect of high temperature on the reaction and the 2- chloroquinoline intermediate was obtained at 78% conversion in a residence time of 30 min at 150 ⁰C using acetonitrile as a solvent. Subsequently, the optimization of the third step in flow to afford the central core intermediate of bedaquiline, 3-benzyl-6-bromo-2-methoxyquinoline, achieved 100% conversion in DMSO/MeOH solvent system at a residence time of 5 min. The effect of temperature, molar equivalence and solvent on reaction conversions could be observed in these steps. The results obtained from this study clearly demonstrated the successful establishment of an efficient flow chemistry protocol that can be used to successfully synthesize all intermediates within the scope of this research. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Mpalala, Anele
- Date: 2022-12
- Subjects: Multidrug-resistant tuberculosis -- South Africa , Tuberculosis --Chemotherapy -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59864 , vital:62455
- Description: SA has a high number of reported cases of multidrug-resistant tuberculosis (MDR-TB). Bedaquiline is a newly approved active ingredient of an anti-tuberculosis drug with high potency against MDR-TB. The limited access to this life-saving medicine to many people in the world has driven a great deal of research effort by the scientific community to find new, better and more practical approaches to this drug. However, many of the reported synthetic procedures suffer from long reaction times, which in turn require many hours of effort by the chemists conducting the reactions. This has prompted us to investigate an efficient process towards the synthesis to produce the key intermediates of bedaquiline using continuous flow technology. Additionally, since there is not much literature on continuous flow synthesis of bedaquiline, this research revealed interesting continuous flow processes towards the drug. Chapter 1: In order to provide insight, the first chapter of this dissertation presents a comprehensive background and literature review on tuberculosis; its pathogenesis, impact, medicines available for the treatment as well as the drug classes with novel mode of action and new chemical entities. Furthermore, bedaquiline is discussed in detail with the various synthetic protocols of the drug. An introduction to continuous flow chemistry is discussed, along with an outline of its advantages and disadvantages. Chapter 2: The second chapter encompasses the experimental procedures utilized for both batch and continuous flow syntheses. The three key intermediates of bedaquiline were synthesized in batch synthesis and these compounds were characterized using 1H-NMR, 13C-NMR and FT-IR spectroscopy. Subsequently, the continuous flow synthesis protocols for the preparations of these intermediates and their optimization are outlined. Chapter 3: The results are explained in this chapter with detailed discussions of the batch synthesis and the continuous flow optimization of each step within the scope of this research. The investigation started with the batch preparation of the primary intermediate, N-(4-bromophenyl)-3-phenylpropanamide via an amidation reaction between 3-phenylpropanoyl chloride and p-bromoaniline. The primary intermediate then undergoes a subsequent formylation and cyclization via a Vilsmeier–Haack reaction to yield 3-benzyl-6-bromo-2-chloroquinoline. The chloroquinoline ii intermediate undergoes a methoxylation reaction to form 3-benzyl-6-bromo-2- methoxyquinoline. Subsequently, the batch protocol was transferred into continuous flow systems, optimized by varying reaction parameters within the synthesis route to achieve the as much yield as possible. The optimization studies showed an improvement in conversions in the various steps with shorter reaction times. The first step was optimized in a 0.2ml microreactor and because of the enhanced safety of flow chemistry, this exothermic amidation reaction was optimised at elevated temperatures to afford the primary intermediate at a 100% conversion within a residence time of 5 seconds using DMF as a solvent with DIPEA as a base. Next, the Vilsmier-Haack cyclization and chlorination was optimised in flow to afford the 2-chloroquinoline intermediate. The ability to use a back pressure regulator allowed for investigation of the effect of high temperature on the reaction and the 2- chloroquinoline intermediate was obtained at 78% conversion in a residence time of 30 min at 150 ⁰C using acetonitrile as a solvent. Subsequently, the optimization of the third step in flow to afford the central core intermediate of bedaquiline, 3-benzyl-6-bromo-2-methoxyquinoline, achieved 100% conversion in DMSO/MeOH solvent system at a residence time of 5 min. The effect of temperature, molar equivalence and solvent on reaction conversions could be observed in these steps. The results obtained from this study clearly demonstrated the successful establishment of an efficient flow chemistry protocol that can be used to successfully synthesize all intermediates within the scope of this research. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-12